*technically* Linux, yes, but in practice people will easily misunderstand, it is confusing unfortunately.
You can try to write something else to clarify what you mean, like how @linmob writes "GNU-like #MobileLinux", see https://fosstodon.org/@linmob/109893712566955547
Note the "GNU-like" there, that's because it's not always GNU, like postmarketOS is not GNU, instead based on Alpine Linux. While PureOS, Mobian, Manjaro etc are GNU/Linux distribtions. 😅