You ask about weaving and mills. In rural areas most weaving was done at home using hand loom weaving machines, such as are still used in the Outer Hebrides in Scotland to make Harris Tweed. These machines were collapsible, so as to be stored out of the way when not needed and for ease of transport should the weaver move home, as they often did, to follow the available work.
Most weavers in Ulster were labourers who earned a bit of extra money by weaving in the winter months when there wasn’t much labouring work required on farms. This meant that labourers in Ulster had a slightly better standard of living than elsewhere in Ireland. It also gave them some ready cash (in a society that mostly operated by barter) for the things that could not be bought by barter, eg a ticket to America.
At one time weavers wove a lot of cotton but the interruption of supplies from the southern US states during the American War of Independence in the 1770s meant they focused on other materials, notably flax (which linen is made from) and which grows well in Ireland in contrast to cotton which won’t grow at all. They did weave other products eg calico and wool as required, but by the 1800s it was mainly linen. Linen made at home was taken to the local linen market and sold there.
As the 19th century progressed, water powered linen mills were introduced all over Ulster. These were faster than home weavers and often made better quality material and so gradually made the home weaver redundant. In addition, the factories also mostly employed women and children (being nimbler and cheaper) so this impacted on male employment too. At a time when farms were starting mechanise and so needed fewer labourers, the average labourer/weaver therefore faced a bleak future and so these combined changes were a major factor in many a labourer’s decision to leave Ireland during the 1800s.
A little more information on this link: https://www.irish-genealogy-toolkit.com/flax-plant.html