If you open an html email, you are being tracked.
If you click on a link in an email, you are being tracked (plain text / html)
Is there any email clients someone can recommend that force plain text in multipart emails? Or convert html emails to be viewed as plain text if the email isn't multipart?
kmail used to be hugely anti html in emails so they may have more options than most for avoiding it.
In thunderbird, which is my current MUA, you can choose View > Message Body As ... > Plaintext and it will display everything it can in plaintext. There's also Simplified HTML and Original HTML as options.
>convert html emails to be viewed as plain text if the email isn't multipart? //
Not sure if that's what thunderbird is doing but it appears to be (if I send a HTML-only email to myself the thunderbird will display it as plaintext).