It depends what you want to apply your linear functions on. If you want to work directly in the source scene light (e.g. photography), then it would make sense to use the inverse OETF. If you are blending graded scenes of emissive light, i.e. a movie, then using the EOTF makes sense. The reason for this is that movies are graded with that EOTF in mind, so by linearizing with that EOTF, you get a resulting linear value as it is intended to be seen by a viewer.
Regardless of what you use for a linearizing function, the more important thing is that you use the correct encoding function afterward, so that you don’t introduce any additional gamma correction. For example, it was common to use a simple squaring function for speed. This gives fairly good results as long as you apply the square root function afterward to restore the original gamma correction. It doesn’t matter if the source is 2.2 or 2.4 gamma encoded or something else, that correction will be preserved. The blending post-linearization will be less accurate, but much better than not linearizing at all.
Regardless of what you use for a linearizing function, the more important thing is that you use the correct encoding function afterward, so that you don’t introduce any additional gamma correction. For example, it was common to use a simple squaring function for speed. This gives fairly good results as long as you apply the square root function afterward to restore the original gamma correction. It doesn’t matter if the source is 2.2 or 2.4 gamma encoded or something else, that correction will be preserved. The blending post-linearization will be less accurate, but much better than not linearizing at all.