Theres no way yet, suposedly the devs are planing to give that option in the future.
Right now im just not loging into lemmy as much as before, the ambience became way more toxic than the first 2 or 3 months i started using it, and i believe its beacause of hexbearians. Lots of bad takes (pariculary genocide apologism) have been thriving on lemmy since they refederated, whuch was ussually trashed before, so i say they are behind that. And when they have more sane takes, they screw them up by telling you to go read Mao, seriously, Mr "Best politics are the ones that come from a barrel of gun" Mao. He was a fucking thug not a great mind of comunism.
I even re-made an account on reddit ffs, and reddit fucking sucks because my comments get ignored into oblivion no mather where i comment, and its not shadowbaning i think.
So my recomendation is try going somewhere else while the option of blocking instances becomes availabe or touch some grass, although grass sucks since it doesnt fight back when asked about politics and it becomes really old very quickly.
Because i like shit just works and i like that it isnt that heavy on defedration with other instances, but thats probably gonna change soon since it seems we are holding votes to defederate from hexbear.
That was the point being made, you shouldn't have to pick one: "let me pick which instances to block instead of choosing for me before I've had a chance to take a close look at them"