A decentralised platform like the Fediverses won't easily work with nation states and their taxes. Even with Wikipedia today, it's not funded directly via any government - but rather by certain universities giving some money to it + all the private doners.
And even if we get that working, power politics will mess this up like so often when things actually get troublesome.
It might be interesting to explore cryptocurrencies as for donations here though. They do have international liquidity and they can't be misused foe power politics.