
There is an undocumented feature on Mastodon that lets you follow a profile's public posts through your RSS feed reader:
The RSS feed address of a public Mastodon profile is the profile's web address with .rss added to the end of it. For example the RSS address of my account is https://social.growyourown.services/@FediTips.rss
This feed will only show public posts though, it will not show any replies or non-public posts.