FWIW, I've done every country in Europe with the exception of Belarus - which has been too difficult to do just now because of the war with Russia and Ukraine as most flights are suspended in and out - you have to go to Dubai or Istanbul and fly in from there. I will do it though, there's a flight I have my eye on that's a very reasonable price it's Edinburgh to one of the London Airports (need to double check what one) then to Istanbul then to Khazakstan (spelling) and then into Minsk, Belarus. It involves over night layovers in Istanbul and Khazakstan but that's fine by me, I love Istanbul and Khazakstan would be an adventure

There was another option for Belarus, last time I was in Lithuania if you can find a taxi driver willing to drive you over the land border after you pay a fee and have an accredited hotel in a certain part of Belarus give you a letter sponsoring you but I think the average time spent at the border to get in and out is 4-5 hours each side so no taxi driver will find it worth his while to do so. I may have some of that slightly wrong, it's complicated - but that's my understanding of the situation, so I left it and have my eye on the Istanbul and Khazakstan flights instead