Usually,‘我在线上课’means ' I take the course online' while ‘我上在线课’means ' I take the online-course'

It took me a while to understand what you mean by these two sentences. I think all the native speakers can understand you without any efforts if you say "我在线授课'. ( I give an online course. ) This is not so tricky as “我在线上课‘ and ”我上在线课“. For a teacher, she/he would say "我在线授课"or "我在网上教学" For a student , she/he would say "我在网上学习"

都很别扭，我们一般说“我在网上上课。”

感觉楼上说的”我在网上上课”不错，还有就是“我上在线课程”吧……感觉我上在线课有一点奇怪呢

都有点别扭，但是我在线上课这个更容易理解。可以说我在上网学习中文