Hello,

I’m not sure if maybe this is due to the humidity level inside my home or not but I just noticed one of the finished oak floor boards on the 2nd floor is beginning to split where the board meets the threshold to a bathroom. I was thinking of using an epoxy wood filler? Is this a good alternative to replace the board altogether? Which filler should I use? Ideally, the product would be an oak-like color. Thank you

The 2 part epoxy that you can but for wood will be good to fill a gap or crack. It will help to glue the pieces together and will not require sealing. You can paint the area if it is not the right color with acrylic paint.
There is another solution to use "pre-finished" color putty in the right color. It is sold at floor distributors and hardwood companies. It is water-based and dries quickly. You don't need to apply finish over it to protect it.
If the board is solid wood it may move in the future depending on the homes humidity. I think the color putty method is easiest and best in the long run. You may need to get two colors to mix together to get the right color. Practice so you can compare the color when it has dried to match your floor.

Thank you. It’s odd because some products are labeled “filler” but based on composition and description might be “putty“. Would something like this be a good option?
https://floormechanics.com/woodwise-pre ... 3-oz-jars/

Yes!