When installing MAAS as a meta-package
> sudo add-apt-repository -y ppa:maas/3.5-next && sudo apt update -y && sudo apt install -y maas

And then removing the metapackage things are indeed are not removed and Temporal Server will continue working because systemd Unit was installed as a part of `maas-region-api` package (debian/maas-region-api.maas-temporal.service) which by the way is listed for autoremove.

> sudo apt remove -y maas
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package 'maas' is not installed, so not removed
The following packages were automatically installed and are no longer required:
  avahi-daemon avahi-utils bind9 bind9-utils curtin-common dbconfig-common dbconfig-pgsql dns-root-data fontconfig-config fonts-dejavu-core freeipmi-common
  freeipmi-tools grub-common ieee-data isc-dhcp-server javascript-common libavahi-client3 libavahi-common-data libavahi-common3 libavahi-core7 libc-ares2 libdaemon0
  libdbi-perl libdeflate0 libecap3 libfontconfig1 libfreeipmi17 libfreetype6 libgd3 libipmiconsole2 libipmidetect0 libirs-export161 libisccfg-export163 libjbig0
  libjpeg-turbo8 libjpeg8 libjs-jquery libltdl7 libnginx-mod-http-geoip2 libnginx-mod-http-image-filter libnginx-mod-http-xslt-filter libnginx-mod-mail
  libnginx-mod-stream libnginx-mod-stream-geoip2 libnss-mdns libprotobuf32 libtdb1 libtiff5 libvirt-clients libvirt0 libwebp7 libxpm4 libyajl2 maas-agent maas-cli
  maas-common maas-dhcp maas-netmon maas-proxy maas-rack-controller maas-region-api maas-region-controller nginx-common nginx-core os-prober postgresql postgresql-client
  pxelinux python3-aiodns python3-aiofiles python3-aiohttp python3-aiosignal python3-anyio python3-asgiref python3-async-timeout python3-asyncpg python3-boto python3-bs4
  python3-bson python3-bson-ext python3-charset-normalizer python3-crochet python3-curtin python3-dateutil python3-decorator python3-django python3-django-maas
  python3-django-piston3 python3-dnspython python3-fastapi python3-formencode python3-frozenlist python3-greenlet python3-h11 python3-html5lib python3-hvac
  python3-iso8601 python3-itsdangerous python3-lxml python3-maas-client python3-maas-provisioningserver python3-macaroonbakery python3-mimeparse python3-multidict
  python3-nacl python3-netaddr python3-paramiko python3-pbr python3-petname python3-prettytable python3-prometheus-client python3-protobuf python3-psycopg2
  python3-pycares python3-pydantic python3-pyhcl python3-pylxd python3-pymacaroons python3-pypureomapi python3-pyvmomi python3-requests-toolbelt
  python3-requests-unixsocket python3-rfc3339 python3-seamicroclient python3-simplejson python3-simplestreams python3-sniffio python3-soupsieve python3-sqlalchemy
  python3-sqlparse python3-starlette python3-tempita python3-temporalio python3-txtftp python3-typeshed python3-typing-extensions python3-uvicorn python3-uvloop
  python3-wcwidth python3-webencodings python3-wrapt python3-ws4py python3-wsproto python3-yarl squid squid-common squid-langpack syslinux-common temporal



If doing autoremove (or when removing maas-region-api) we can see that Temporal is stopped and removed:
> sudo apt autoremove -y maas

Removing temporal (1.22.5-0ubuntu1) ...

> journalctl -fu maas-temporal
Apr 01 13:33:38 foo systemd[1]: maas-temporal.service: Deactivated successfully.
Apr 01 13:33:38 foo systemd[1]: Stopped MAAS Temporal.
Apr 01 13:33:38 foo systemd[1]: maas-temporal.service: Consumed 1min 51.776s CPU time.


However, we don't remove Temporal config:
root@foo:~# ls -al /var/lib/maas/temporal/production.yaml
-rw------- 1 maas maas 1915 Apr  1 12:46 /var/lib/maas/temporal/production.yaml