Telit LE910S1 support in ModemManager is available since the second bugfix release of the 1.18 series (1.18.4), released in late November.
Telit LE910S1 support in Linux kernel
ModemManager relies on the serial ports created by the option driver for compositions 0x7010 and 0x7011, whose support was added to the Linux kernel since v5.13-rc4.
Recently also the firmware upgrade device 0x1bc7:0x9200 has been added through patch “USB: serial: option: add Telit LE910S1 0x9200 composition“, available since kernel v5.16-rc3.
ModemManager Merge Request !668
Those who are unable (or do not want) to upgrade to 1.18.4 can refer for backporting to ModemManager merge request !668 which is made of three short commits implementing support for the modem.