Yes, a maternal uncle can support you. The money does not have to come from a parent. Any relative can be a supporter as long as the relationship is stated and documented.
His letter has to carry four things, and this is where most of them fail: his occupation, his relationship to you, how many dependants he has, and the amount he is supporting you with. Attach a copy of his photo ID. The dependants line is the one people leave out, and it is the line that tells an officer whether his support is realistic on top of his own family.
On the amount: from 1 September 2026 IRCC's figure is CAN$23,448 for one person for a year, and that is living costs alone. Tuition and travel sit on top. So the number you are working towards is first-year tuition plus 23,448 plus flights both ways, shown without counting any work in Canada.
Rental income counts in its own right, with the lease and the bank entries that show the rent arriving. Employment income is pay slips or an employer letter plus the deposits. Bank statements should cover six months, including the month you apply or the one before, and they have to show where the money came from, not just a balance. Agricultural income is the one to think about: land that produces income is not the same as income an officer can follow. It has to arrive in an account and be traceable to the land, otherwise it is a number in a sentence.
Two things people rarely ask. There is no minimum bank balance, so anyone quoting you a figure is inventing it. And where a country restricts moving money abroad, you have to show you can actually export it. Check what applies in Nepal before you build the whole file around funds that cannot leave.
Nobody can tell you from a message whether your profile is "sufficient", and be careful with anyone who will. What is fixed is what has to be proven and what each document has to contain. The rest is an officer's judgement.
This is community experience, not legal advice. For your own file, speak to a licensed consultant or lawyer.