There is no tahiyatul masjid as it is not a masjid.
If the Iqamah is called, one must join the prayer and this would suffice for tahiyatul masjid

On fridays we gather in a gym to pray jumuah as our community mosque is small, are we obliged to pray tahiyatul masjid since it is a gym? And how does one pray tahiyatul masjid at the time of maghrib? In the masjid where I pray they start the salah immediately after adhaan