I'm sure this is worse than using lastpass in some way
but for the past couple years I've just generated and forgotten 90% of my passwords. the final 10% I keep in a password manager. But if the service isn't really that important I just use the 'forgot my password' to change and generate a new password every time I need to login
This works if the account doesn't have 2FA. On my last side project app users can login only via email OTP. There are security downsides with that, someone can send phishing link and use OTP submitted to the fake site, but the app doesn't store anything sensitive (it's a game which tracks your progress) so I guess it's not a major security risk.
But the phone number you have is not 100% in your control. I had AT&T flub something and I lost my number and they assigned me a new one (I was chanting my plan just after they did some merging with someone). Granted its unlikely but I would still use defense in depth and not have password reset be my only login method.
It's also why I always opt for 2FA that's within my control: a security key, TOTP, or an email address on a domain I own. That last one is the weakest, since I own the domain as long the registrar says I do but it's better than a corporation I can't get support from if my email account is locked for any reason.
Manually forward the magic mail to an address which you can use on your laptop/desktop for that purpose only.
Even though i understand your consideration of separating regular access and reset onto different devices, im am still more sceptical about smartphone security than anything else. What happens when someone gets access to your phone? They could redirect and use the magic mails too.
but for the past couple years I've just generated and forgotten 90% of my passwords. the final 10% I keep in a password manager. But if the service isn't really that important I just use the 'forgot my password' to change and generate a new password every time I need to login