Under the vaulted brick arches of a contemporary art center in central Kyiv, a soldier in military green gave a reading of his own poetry, far from the front lines of the war he has been fighting since Russia’s invasion of Ukraine.

Like many other soldiers, Pavlo Vyshebaba, 37, a platoon commander with the 68th Brigade, had long been collecting donations to procure supplies for his unit, in his case using his poetry as an appeal.

But donations, which once flooded in via the web, have been lagging lately as the war drags on. Mr. Vyshebaba recently took two weeks off from the war to give readings around the country in a push to ramp up contributions in person.

“I saw that the fund-raising on the internet at the beginning of 2023 stopped being effective, that maybe my audience was exhausted and we didn’t have victories for a long time,” he said. “But we still needed all this stuff.”

In the last two weeks, he has collected more than $100,000, which will go directly to supplying soldiers at the front lines he will return to days after this final poetry reading at a Kyiv book festival.

Since Russia launched its full-scale invasion of Ukraine last year, many Ukrainian military units have relied heavily on donations and charitable funds to supply their troops with much-needed supplies like first aid kits, body armor, vehicles and even drones.

People and groups from around the world rallied to Ukraine’s cause, providing valuable aid that could find its way to the front lines far more quickly than goods coming through often cumbersome government channels.

Sixteen months later, that enthusiasm seems to be waning, based on interviews with charities and soldiers who have been fund-raising. Ukrainian soldiers on the front lines say that donations now are less frequent, and that people seem to be moving on from the war, even though the conflict is just as tough and bloody as ever and casualties continue to mount.

This has left some soldiers trying to raise money on their own, often through unconventional means: selling paintings or memorabilia from the front lines, like pieces of downed Russian drones; offering to add personalized messages to artillery shells for a fee; and, in one case, a soldier raising money from a viral video he made of himself almost single-handedly repelling a Russian advance.

The wartime musings of Mr. Vyshebaba, who has written poetry since childhood, have proved popular. He has collected enough money so far for his brigade to buy drones, radios, Starlink communications devices and anti-drone weapons, among other supplies, he said.

“When large batches of drones, Starlinks, pickups began to arrive — the guys from those units were coming to thank me or the commanders wrote to me,” he said of earlier funding drives.

Now, though, in the back of the pickup truck of a supply sergeant, who withheld his name for security reasons, were the usual military armaments: an antitank guided missile launcher, rocket launchers and ammunition boxes.

But the weapons no longer worked and the boxes were empty. This once-lethal matériel, the sergeant explained, had a different purpose, headed not to the front lines but to the Salvador Dalí Academy of Contemporary Arts in downtown Kyiv. There, it would be decorated and auctioned off to raise money for his embattled brigade. He said he hoped that a celebrity like Bon Jovi would buy the missile launcher for an exorbitant fee.

“Most people are just tired of this war already,” said Ruslan Zubariev, a soldier from the 92nd Mechanized Brigade, who became a one-man fund-raiser after he used a helmet camera to film himself stopping a Russian advance nearly alone. “Civilians don’t realize that if they’re tired and stop donating, it doesn’t mean the war is over.”

Mr. Zubariev, 21, was in a unique position in February after his video, which showed him killing several Russian soldiers and stopping an armored vehicle with a rocket launcher near the Russian-held town of Svatove, went viral. His unit, up to that point, had relied mostly on outside volunteers bringing in equipment. After uploading his video he gained thousands of Telegram and Instagram followers practically overnight.

So Mr. Zubariev monetized his battlefield valor, a move he saw as necessary since the military seemed unable to supply much of the equipment they needed to fight, he said in an interview.

“We repair cars, we repair equipment, we repair weapons. We repair this, this, this, this, this — generators, fuel, all of it. It all breaks down,” he said. ”We don’t get that stuff issued to us. We buy it all with our own money.”

Fund-raisers typically buy the goods directly from suppliers, sometimes using intermediaries abroad. They can often bypass the slow bureaucracy and send them to specific units or soldiers, allowing them to be more nimble than the military’s own distribution system.

Even the big, established charity and aid groups are struggling with flagging interest in the war effort. Oleh Karpenko, the deputy head of the Come Back Alive foundation, one of Ukraine’s biggest donors to the military, said fund-raising was becoming more and more difficult.

Come Back Alive was the first charity in Ukraine that had a license to purchase military goods, including lethal weapons, directly from manufacturers.

Last year, the charity raised nearly $177 million and supported 580 military units with hundreds of vehicles, thousands of pieces of thermal imaging equipment, drones, radio stations and weapons, according to the organization’s annual report.

Mr. Karpenko said that while they did not have figures yet for this year, they expect them to fall short of that mark, because of dwindling international interest and a more challenging landscape at home.

“The economic situation in the country is becoming more difficult as well, than it was a year ago,” he said.

The charity communicates directly with troops to assess their needs and expedite supplies to them.

“The state is a big bureaucratic mechanism which moves very slowly, but some needs are super urgent. Our benefit is speed,” he said. “We can procure without hundreds of approvals from 15 different offices. We can receive an agreement today, sign it and have a truck of machine guns in three weeks. The state cannot do this.”

In the hallway of the foundation’s new office on the outskirts of Kyiv, the remains of downed Russian drones sit wrapped in plastic, ready to be shipped to partners eager for a token from the front line, Mr. Karpenko said.

Smaller donors are also feeling the crunch. Les Yakymchuk, 30, has been collecting first aid kits since the start of the war with his charity, UA First Aid, but he said it had grown increasingly difficult to maintain interest.

“If you are fund-raising for a year, or more than a year, and you are talking about the same stuff in the same way, people start getting tired of this, tired of sending money,” he said. His group has tried to revive interest in various ways, like sending tokens from the battlefield, such as flags signed by the members of a battalion.

He said many requests for supplies still came directly from soldiers hoping to bypass the often complicated logistics of official government channels.

“Everybody is still calling us,” he said. “But this is war, and during the war nothing can be perfect.”

Oleksandr Chubko contributed reporting from Kyiv, and Natalia Yermak from Kharkiv.