Third-party exFAT support did exist before 2019, but vendors had to pay a licence fee to Microsoft. Apple apparently paid the fee. Regarding Linux, exfat-utils

Third-party exFAT support did exist before 2019, but vendors had to pay a licence fee to Microsoft. Apple apparently paid the fee. Regarding Linux, exfat-utils only provided limited functionality. The kernel mainline lacked a native exFAT driver. Mounting exFAT volumes was possible only through FUSE (with all its shortcomings).