@inthehands if you have a bank account somewhere that also owns a brokerage most have low cost/self managed trading options (for example if you bank with Bank of America you can open an account at Merrill Lynch pretty easily. May not be the most ideologically pure but may be easy if you already have the accounts.
(fewer credit unions or b corp banks have brokerages)
I'm reasonably happy with Charles Schwab but not sure their minimums but generally decent (relatively for their industry)