Generally Bitcoin has solved this by social and denominative means — definitionally if a majority of miners sign a stream of blocks that ‘break the rules’ then,

Generally Bitcoin has solved this by social and denominative means — definitionally if a majority of miners sign a stream of blocks that ‘break the rules’ then, that is the truth and the miners have chosen new rules. Socially if this is signing a block with a bug, miners have historically colluded to rewrite history. If on the other hand the new blocks embed protocol changes, then we move to names: is it still ‘Bitcoin’? If not then there is a hard fork with a new community. This is the BCH, BSV and ETC story. The answer to your question about Algorand is probably similar, unless the scheme has some novel mechanism to prune hard forks, or a way to radically include them.