In theory yes. But I personally wouldn't recommend it. I finished the last ~2 years of my PhD remotely due to the pandemic and found it really tough going. No in person chats with colleagues and people in your department was very detrimental to my development, think. The amount of knowledge you get from simply being around other researchers shouldn't be underestimated. If you get stuck, there's nobody on hand to help you, unlike being in an office environment. You don't get the benefit of getting ideas from others.
You’ll also just miss out on a lot of the fun that goes on with being a PhD student in a university - I had a really great time in the 2 years I was on site.
That’s not to mention the mental toll that kind of isolation takes on you, but different people will deal with that differently. If you have a partner or housemate or something who works at home as well, it can make it a lot more tolerable.
i did my PhD in a lab with no other grad students and no postdocs, at a time when the institution i was at had little to no bioinformatics infrastructure, dedicated faculty, or coursework.
it was for those reasons as close to "remote" as one could get ... despite being at a major academic institution.
there were so many nights when i would have benefited from having colleagues physically present, or just from having met collleagues at similar levels of training.
my mentor was incredibly supportive, but the bottom line is that despite everything he did i probably would have had a better education if i had surrounded myself with other trainees, not to mention post docs.
can you get the work done and make a unique contribution to a field on your own? can that be done? of course. but is it the best option of any available to you? very different question.
I don't think any program, in any discipline, can maintain the required rigor and deliver the PhD remotely. Not to mention that it wouldn't be fun, nor would it allow personal interactions that are part of the process.
A very large fraction of it, yes. Presumably, you already have a masters, as most phd programs now demand that, so there aren't a lot of courses to take (maybe 6-8) and many of them will be online. Then if you can get out of the RA/TA duties and pay your own tuition, there's just a dissertation to propose and defend. Most programs won't openly admit this is possible but COVID and the general decline of academia has radically changed how they operate in reality.
At my institution this is not possible. We have substantial clure requirements, and the courses are in person as a matter of university policy. Once you're done with courses, there's a lot more flexibility at the discretion of one's advisor but there are 2 things to consider. First, while many advisors are happy to approve an extended remote period, I'm not aware of any that would allow remote completion for the duration of the degree (additionally, we have requirements that certain exams, like the defense, be in person). Second, depending on where you do the degree and your citizenship etc., there are residency requirements that may require you to reside in a particular region for a certain fraction of time (even if you aren't otherwise required to be on campus). In short, doing there degree partly remote may be possible if you find the right advisor and both agree on this, but at many institutions, fully remote isn't possible, and I don't see that changing any time soon.