advice does not exist in a vacuum, it exists in the real world and should be compared to alternatives, honestly
the risks of mstr in a brokerage account: trusting multiple corporations, trusting the government
if you are fine with that threat model then bitkey has less risk, is easy, and has inheritance built in
if you want to take it up a step then single sig with a seed kept in multiple locations is more secure, and still relatively easy with popular hardware wallets
if you are a public figure or have a more advanced threat model for some other reason then it could be worth it to learn how to use multisig
