6.0 is LTS, and so is 5.2. Those are both in long term support, with security fixes only.
7.x will have active development with bug fixes, security fixes and features for the next 12 months, and then will have security fixes only until the end of Q4 2027 when it’ll come to the end of security support.
While 7 is our new major release, most folks are waiting on 5.2 until the end of security support (end of Q2 2026) and then transitioning over to 7 directly, and skipping 6. Failing that you can get Extended Long Term Support for 5 to give you an extra two years of using 5, or one year for using 6, if you can’t update yet.
Read about the reason for our shorter release cycle on 6 and generally how we manage support periods here: Introducing Mautic's new release strategy: Long Term Support for enhanced stability and continuity - Mautic.