IBKR and Saxo Bank are the way. avoid etoro / xtb and other "commison free" shit scams.

No banks with direct trading (except Saxo, they operate in this region and have also czech support). You will pay health insurence under 100 eur / month as unemployed. For tax purposes it is best to contact some tax advisor company, there is no automatic taxation by brokers and you will also have pay the health insurence on your realised gains. Based on your description, it sounds like the best option will be to create own "sro" company (something like gmbh) and you will be employee of this company and will hive it the loan in form of your portfolio. but any tax advisor will give you better overview. I have good experience with "palkovic sro" (google them). your tax will be 21% (tax on crypto gains is higher).

btw both tatra bank and slovenska sporitelna are good, tatra have better private client services (you will qualify for private client by holding "unspecified" average amount of money on your account for like 12 months, think its around 30k but not sure, also they will like you and give you higher internal score when you use their credit card but they have funny low limits - like 5k/month for gold visa, its good for any future requests or loans or whatever you will need)

good luck do pici!