Frozen Rivers in the past have generated only in snow-covered biomes, but since 1.18, they can generate like this inside of regular taiga biomes where one would normally expect a regular river biome to generate instead. 

Frozen River Image 1 seed:
1648003335076685642
Coordinates:
/tp @s 2227.25 166.55 748.21 241.48 85.17

Frozen River Image 2 seed:
2821429629522491957
Coordinates:
/tp @s 4166.75 162.75 -5282.14 509.98 73.50