Remember: not your keys, not your bitcoin! If you cannot even send bitcoin to an address that you are in control of (like you can from an exchange to your own wallet) – you don’t actually possess/control any bitcoin.
Also, you don’t get any coins from potential forks.
Please let’s keep that in mind and not recommend these options for beginners (unless withdrawals are allowed). It’s highly misleading and unethical in my view.
Revolut: (https://community.revolut.com/t/bitcoins-and-others-cryptocurrencies/10993/3) (https://community.revolut.com/t/send-bitcoin-eth-ltc-to-and-from-revolut/18427/4)
(also can confirm as Revolut user myself)
Robinhood: I couldn’t find any infos on their site itself, but the comments in this thread suggest that withdrawals in bitcoin are not possible, for the time being at least: https://www.reddit.com/r/Bitcoin/comments/7wql3o/robinhood_listed_as_the_app_of_the_day_on_the/
Robinhood’s official FAQ doesn’t mention withdrawals, only that bitcoin deposits are not allowed: https://support.robinhood.com/hc/en-us/articles/360000088663-Crypto-Transfers-Deposits
This review site says that withdrawals to external wallets are not allowed (scroll down, under “pros and cons”: https://www.finder.com/robinhood-crypto-review
edit: I found posts with users saying that their Robinhood in-app FAQ says withdrawals are possible after KYC verification (bank account, ID selfies etc): https://imgur.com/a/FTYRm
Their website FAQ doesn’t make any statement on this though, so mixed reports so far. Would be good to hear from users with direct experience, if they have been able to withdraw bitcoin.
edit2: answer from Robinhood support, not really helpful:
> Hi there,
> Thanks for reaching out.
> We don’t have any additional information about Robinhood Crypto at this time, but look forward to sharing more details soon.
> In the meantime, you can learn more about Robinhood Crypto in our blog, or by visiting our Help Center.