Twitter's help page [1] claims you can verify up to 10 accounts with the same phone number, but in reality there's a few weeks cooldown period after 2 accounts where you won't be able to reuse the same number even if you remove it from all accounts. You used to be able to verify 4 at once by removing the number from each account right after verification, but now they're stricter and removing the number right after verification rather than waiting a few weeks is very likely to get your account locked and asking for phone verification again immediately.
You can use Google Voice (if you live in the US) or getsmscode.com, though. I've used the latter a lot for multiple sites and it's mostly reliable, better than free alternatives and it only has a very minimal cost ($0.1-$0.5 per verification text). Although it should be noted that sometimes Twitter will randomly force you to re-verify your phone number a while later, and the numbers on this site don't last forever (the US ones generally last for at least a few months, while Chinese ones likely won't work the next day already), so your account may be locked forever unless you manage to successfully appeal to Twitter (which can take anywhere between an hour and 6 months to get a response, whether it is positive or negative).
Thanks. Yeah, had lots of problems when making my new account recently. It got constantly locked. Then support unlocked it but it got locked automatically a few hours later each time. I'm not exactly running a troll farm here, I get why they do it, but very annoying. Half the fun of twitter for me is the niche accounts. Like World Bollard Association for instance (not mine). But making these gets harder every day.
You can use Google Voice (if you live in the US) or getsmscode.com, though. I've used the latter a lot for multiple sites and it's mostly reliable, better than free alternatives and it only has a very minimal cost ($0.1-$0.5 per verification text). Although it should be noted that sometimes Twitter will randomly force you to re-verify your phone number a while later, and the numbers on this site don't last forever (the US ones generally last for at least a few months, while Chinese ones likely won't work the next day already), so your account may be locked forever unless you manage to successfully appeal to Twitter (which can take anywhere between an hour and 6 months to get a response, whether it is positive or negative).
[1]: https://help.twitter.com/en/managing-your-account/phone-numb...