The best replacement for alpha channel is clipping path.

The best alternatives to alpha channel are rated as following:
★★★★★  clipping path
★  layer mask

Your alternative for alpha channel is not listed? Suggest!
Speaking about alpha channel, one probably shouldn't forget about prores.

Other search terms related to alpha channel and their ratings are:
★★★★★ prores
★★ avi
★ bmp
★ video
You have in mind a companion for alpha channel and it is not yet here? Propose!



Google Trends

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alpha channel
clipping path
layer mask