The earliest Catholics would have been Jews. The Passover liturgy, which is the inspiration for the liturgy of the Eucharist as it was done at the Last Supper, is still practiced today on an annual basis by Jews.
The Passover liturgy itself is a derivation of sorts of the weekly Sabbath (“Shabbat”) meal held on Friday nights in a private home. Nowadays, the wine is raised in a cup and blessed first, then drunk by everyone at the table out of the same cup or each person’s individual cup.
Hands are then washed in ritual fashion with a wash cup, two loaves of bread are pressed together and raised by the person at the head of the table, blessed, and then sliced. Bread is then distributed to each participant before eating a festive dinner meal. Some traditions include a ritual “slice” of the bread before the blessing of the bread, but the knife does not touch the bread. You can read the entire ritual in most traditional Jewish prayer books.
My point being that you would need to research the Jewish practice at that time to know how the earliest Catholics - Jews at the time - received the Body and Blood of Christ. I believe it would not have been done so kneeling, on the tongue, but rather at a private dinner table, seated, and with blessed bread distributed in the hand.
My guess - I would have to read up on this - was that the first “Masses” were held in private homes before these Masses gravitated to more public settings. Given the open hostility to Christ and Christians at the time, much of the breaking of bread and wine done in Christ’s name was probably held in private homes for privacy and security reasons. Right after Christ was crucified, anyone celebrating a large public display of breaking bread and wine in Christ’s name would have been targeted by the authorities.