Every commentator that I examined (quite a number) agree that the home that serves as the meeting place for the local congregation is that of Philemon. The reason for this is rather simple:
- The opening greeting in the letter to Philemon is primarily addressed (obviously) to Philemon
- Paul then addresses those who orbit around Philemon, his relatives and friends and Gospel workers
- finally, the church that meets in Philemon's house
It would be truly extraordinary if in a letter to Philemon, he begins a salutation to people only distantly related to Philemon such as a church that met in (say) the home of Archippus! If Paul wanted to salute such folk he would have done so near the end of the letter as was done in Col 4:15.
Note the comment from Gill -
and to the church in thy house: not in the house of Archippus, but in the house of Philemon;
Similarly the Cambridge commentary -
Philemon’s house was the Christian rendezvous of Colossæ, and his
great room the worship-place.
Thus, the opening greeting could be set out more clearly as -
To Philemon our beloved fellow worker,
- to Apphia our sister,
- to Archippus our fellow soldier,
- and to the church that meets at your house:
Thus, Paul begins this touching letter to Philemon with the triple greeting to three sets of people closely associated with Philemon.