The required TimescaleDB version should not be increased so quickly, because if you are stuck with Azure, you will only get what Microsoft offers, which is always far behind the actual releases.

whupper, it is still possible to set AllowUnsupportedDBVersions=1 in zabbix_server.conf to override version check and use an unsupported TimescaleDB version. Would it solve the problem?

If Zabbix can still work with the older version of course, but I think there is also a absolut minimum version which is required and where Zabbix can't work under no cirumstances with a version lower than that. So it depends which version from TimescaleDB this will be in Zabbix 8.0. Actual there is still only Timescale 2.10 available for a Postgresl15 DB in Azure.

TimescaleDB 2.20 will be the minimum supported version (soft limit).

https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/include/zbx_dbversion_constants.h

Hard limit is what you called the absolute minimum. It is not explicitly documented, but Zabbix would not just start if this requirement is not met. AllowUnsupportedDBVersions=1 does not affect the hard limit.
Soft limit is what we call MIN or MAX supported version, which is also documented at this page https://www.zabbix.com/documentation/current/en/manual/installation/requirements#required-software

/* ZBX_*_MIN_VERSION - hard limit */
/* ZBX_*_MIN_SUPPORTED_VERSION - soft limit */
/* ZBX_*_MAX_VERSION - soft limit */

#define ZBX_TIMESCALE_MIN_VERSION 20001 // no change to hard limit within this task
#define ZBX_TIMESCALE_MIN_VERSION_STR "2.0.1" // no change to hard limit within this task
#define ZBX_TIMESCALE_MIN_SUPPORTED_VERSION 21300 // will be changed to 22000
#define ZBX_TIMESCALE_MIN_SUPPORTED_VERSION_STR "2.13.0" // will be changed to "2.20.0"

Also the soft limit will be changed for PostgreSQL within this task.