The scenario you're describing sounds like the opportunity is really, really ripe for anti-immigration parties (or at least parties more skeptical of immigration), but to my knowledge SF does not seem to be dramatically different than the others.
A few years ago that would've been true, but today they might as well be taking their lines from Matteo Salvini or (irony of ironies) UK Conservatives.
Mary Lou McDonald: Ukrainian refugees not working in ‘critical’ jobs should not automatically be allowed to stayUkrainian refugees who are not working in ‘critical’ jobs should not automatically be allowed to remain in Ireland beyond March 2025, Sinn Féin leader Mary Lou McDonald has said. In a hardening of party policy, the Sinn Féin leader said it was a ‘mistake’ to afford special status to Ukrainians. She said that those without key jobs should be made to apply for asylum – and called for deportations to be expedited.
Vast majority of the EU’s Asylum and Migration Pact is not in Ireland’s interests – Pa Daly TDSinn Féin are opposed to open borders. We believe that Ireland needs a well-managed migration system – one that is fair, efficient and enforced. [...] We simply do not have enough beds in our IPAS system to continue accommodating people who should be in other EU countries. [...] We oppose opting-into the remainder of the measures. They are better dealt with at a national level. This is an important issue of sovereignty. It must be for an Irish government to decide on key aspects of our immigration system, including rejecting unsuccessful applicants sooner, compiling our list of safe countries so those who are not genuine asylum seekers can be rejected and to decide what countries Ireland should take refugees from. These are not matters for the EU to dictate to us.