Which heating boiler as a replacement?

Hello everyone, I have a question regarding the replacement of the existing gas boiler. Unfortunately, I have zero knowledge in heating technology and do not want to be wrongly advised or sold something by a gas-water installer. Currently, I have a Vaillant VKS 23 E gas boiler, built in 1994. This device had maintenance yesterday and the operation of the device is flawless. Now the company employee pointed out that the chimney sweep might shut down the boiler due to its age and that I should consider a replacement in the next few years. I do not need a boiler for hot water, as the hot water tank is operated by solar. Question: Which technology should I choose? What heating capacity do I need as a replacement? It is a multi-family house.

If the device is not defective and the values are maintained, he cannot shut anything down there. So only start worrying again if the thing breaks (or starts acting up). Before that, a replacement is definitely not worthwhile.

Values still fit perfectly. The chimney sweep conducted the measurements a few weeks ago.

Then don't let yourself get confused!