I use encrypted disk images for this purpose myself, but I’m firmly on the Apple device path. There is an iOS/iPadOS app called Disk Decipher that can access encrypted Mac disk images, but iOS natively does not support them.
If I worried about accessing on other desktop/laptop platforms (Windows, Linux) I’d use either veracrypt or perhaps aescrypt, but probably Veracrypt because, again, Disk Decipher supports that on mobile platforms.
Disk Decipher is free but I’d suggest the in-app payment of $7.49 to support writing APFS, NTFS, and HFS file formats. (It can read them for free.)