I do not own minecraft outside my ps4, I know I can't play either Windows 10 or Java with that purchase. However, my primary computer is Linux and only supports the Java edition, and its past the deadline to get a redeem code for windows 10 edition if I purchase the Java Edition. Can I purchase the Windows 10 edition and use that purchase to login and play on the Java edition?
No, You are unable to buy Windows 10 (Bedrock Edition) and get Java Edition for free.
However, if you bought Java Edition before October 19th 2018, you are able to redeem a free copy of Bedrock Edition on https://mojang.com/.
Following link details further. https://help.mojang.com/customer/en/portal/articles/2064007-minecraft-for-windows-10