Digital modes are allowed over FRS radio, without a license. Here is a test I performed, sending text over an unmodified radio using the data mode called BPSK31.

https://cdn.masto.host/mastjohn1126com/media_attachments/files/116/099/159/162/674/108/original/428480a0527515b5.mp4

From the FCC rules

§ 95.531 Permissible FRS uses.

"FRS units may transmit digital data" ... "containing a brief text message"

A text message that is "brief" is a vague specification, defined without a numerical value of time or length of text. So it is a subjective judgment on how long the transmission may be.

The data modes allowed are also not defined. The FCC makes no mention of “prohibited digital modes”. So I assume any digital mode may be sent over an unmodified FRS radio with a voice transmission.

FRS units may be used for one-way communications that are emergency messages, traveler assistance communications, voice pages or brief equipment tests."

Equipment tests are also allowed over FRS.

And in an emergency, any mode of transmission is allowed over any radio, even without a license, if it is for "immediate safety of human life or protection of property".